1. Field of the Invention
The present invention is concerned with new compositions that can be formed into cured layers having high electrical conductivities and high light transparencies.
2. Description of the Prior Art
In general, polymer coatings are non-conductive, electrical insulators. However, electrostatic charge can accumulate on these coatings, causing electrostatic discharge (ESD) damage. This problem can be solved by imparting conductivity to the coatings. Electrically conductive coatings are needed for consumer, industrial, military, medical, and other applications. In one such conductivity-imparting process, metal particles such as silver or conductive carbon are added to polymer coatings to make them conductive. While this will render the coatings electrically conductive, it will also make them opaque. This is undesirable in many applications where the coatings need to be transparent. For example, it is imperative that these coatings be transparent when used on airplane windshields and canopies and in flat panel displays and other optoelectronic devices.
In another process, an intrinsically conductive polymer (ICP) can be added to the photopolymer coatings to make them conductive. The transparency of the coatings could generally be maintained if the amount of ICP added is small, however, it has been necessary to add larger quantities of ICP to obtain sufficient conductivity. The advantages of using photopolymers as coatings are their ability to cure rapidly at ambient temperatures and their ability to undergo direct patterning without using a photoresist and etching step.
In one prior art method of forming ICP/insulating polymer composites, UV-curable photopolymer/polyaniline composites were obtained by blending multifunctional acrylates, a photoinitiator, and a polyaniline dispersion, which was doped with special dopants. However, a high proportion of polyaniline was required to obtain significant conductivity, and this causes thick coatings to have a dark green color.